The invention relates to an optical instrument and in particular to an endoscope.
The invention more specifically relates to an optical instrument, having a shaft and having an interchangeable head that is detachably connected to the distal end of the shaft at the coupling point, and having, furthermore, a first transmission system for transmission of illuminating power in distal direction and having a second transmission system for transmission of image information in proximal direction, the first transmission system and the second transmission system passing through the coupling point.
Such an optical instrument, in particular an endoscope, is generally known through its use, the interchangeable heads being interchangeable objectives or supplementary lenses in the case of known instruments without the invention being limited thereto.
Although the present invention is described using the example of an endoscope, the invention is not limited to an endoscope, but rather can be used generally in optical instruments or devices.
Endoscopes are used for medical purposes, on the one hand, and for technical purposes, on the other hand. In medicine, endoscopes are used in minimally invasive surgery for visual control of operations. In the technical field, endoscopes are used to investigate cavities that are difficult to access, in particular to investigate operating cycles in engines, turbines and in reaction chambers, including during their operation.
Furthermore, known endoscopes include those with a rigid shaft and those with a flexible shaft, it being possible for endoscopes with a flexible shaft to be introduced to the place of use through winding paths, and also various viewing directions being made possible by means of a deflecting mechanism.
Endoscopes are usually fitted with a first transmission system for transmission of illuminating power in distal direction, and with a second transmission system for transmission of image information in proximal direction. It is normally incoherent fiber bundles, that is to say optical waveguides that are used as the first transmission system for transmitting illuminating power. However, within the meaning of the present invention, illuminating power is also understood as electric power used to feed a light source on or in the endoscope. In the case of endoscopes, the transmission system for transmitting image information comprises either lenses, coherent bundles of optical fibers, that is to say so-called image waveguides, electric lines that conduct in the proximal direction electric signals generated by a distally arranged image pick-up, lightwave data lines, or teletransmissions by means of temporally modulated radio waves or temporally modulated light.
With known endoscopes, there is usually also present at the distal end of the shaft of the endoscope an imaging optics that images the space to be observed onto the start of the transmission link, for example onto a fiber bundle.
The imaging optics used, which is not exchangeable, fixes the direction of view and the field of view. In order to configure an existing endoscope in a more versatile fashion with regard to direction of view, field of view and working distance, endoscopes are currently being offered with interchangeable heads in the form of interchangeable objectives, it being possible to vary the direction of view, the field of view and the working distance by selecting an appropriate interchangeable objective. The possibilities of use of the endoscope, which is not infrequently very expensive, can be widened in this way by keeping various interchangeable objectives at the ready.
The interchangeable objectives of the known endoscopes, in particular in accordance with U.S. Pat. No. 4,706,653, are not independent optics, but are designed only as supplementary lenses of telephoto or wide-angled nature such as are known from photography. The interchangeable objectives of the known endoscopes also include, for example, deflecting optics in order to be able to switch over from a straight ahead direction of view without interchangeable objective to a lateral direction of view with an interchangeable objective coupled on. In the case of interchangeable objectives of the known endoscopes, there are also included, if appropriate, in addition to the imaging optics optical waveguides and optical elements for illumination that adapt the illuminating light to the field of view.
In order to avoid the leakage of illuminating light into the observing optics at the coupling point, in the case of the known endoscopes a staircase-like spatial graduation at the coupling point has mostly been provided between the light transmission system and image transmission system.
A substantial problem with endoscopes that are fitted with interchangeable objectives is the risk of an overlooked loss of the interchangeable objective when the latter becomes undesirably loosened from the distal end of the shaft of the endoscope. In the case both of endoscopes for medical purposes and of endoscopes for technical purposes, an overlooked loss of the interchangeable objective in the area of observation, that is to say in the case of medical endoscopes in human or animal bodies, and in the case of technical endoscopes, for example, when the endoscope is used in aircraft maintenance during engine inspection, is associated with devastating consequences in some circumstances.
Various antiloss safeguards such as bayonet closures, subdivided threads, subdivided left/right threads and thread/bayonet combinations have been developed to solve this problem in the case of known endoscopes.
Apart from the fact that such antiloss safeguards render it difficult to mount the interchangeable objectives on the shaft of the endoscope because of the small dimensions of the interchangeable objectives in the case of endoscopes, such antiloss safeguards do not completely solve the problem of the overlooked loss, since in the event of failure of the antiloss safeguards it is possible nevertheless for the interchangeable objective to come loose from the shaft of the endoscope without this being noticed.
As already mentioned previously, optical instruments, in particular endoscopes, are also known in the case of which the transmission system has for the purpose of proximal transmission of image information at least one electronic image pick-up that is arranged in the region of the distal end of the shaft such as is known, for example, from U.S. Pat. No. 5,379,756. In this known endoscope, an imaging optics is connected upstream of the image pick-up, which is not exchangeable, at the distal end of the shaft. This endoscope has no interchangeable head. Document U.S. Pat. No. 6,184,923 discloses a comparable optical instrument in the form of an endoscope having an electronic image pick-up, this endoscope containing at the distal end an interchangeable head that has an imaging optics for imaging the area of observation onto the image pick-up. Thus, in this instrument only the imaging optics is exchangeable, but not the image pick-up. However, the production costs of the shaft with permanently integrated image pick-up or a camera are increased thereby.